Technical Field
The present invention generally relates to a structure and manufacturing of a power semiconductor device, and more particularly relates to a structure and manufacturing of a semi-insulating field plate.
Related Art
The present invention will be described in the structure of a power diode. However, it should be understood in the following description that, the present invention is equally applicable to the structures of other power semiconductor devices, such as metal oxide semiconductor field effect transistors (MOSFET), bipolar junction transistors (BJT), insulated gate bipolar transistors (IGBT) and thyristors.
Semi-insulating field plates have been widely used in power semiconductor device structures. The basic function of a semi-insulating field plate is to provide uniform electric field distribution below the plate in the off state of the device, and this contributes to improving the breakdown voltage of the power semiconductor device. However, the semi-insulating field plate usually requires patterning, which needs an additional etching step [1] which increases the manufacturing cost. The etching step may be skipped by depositing an amorphous silicon layer as a semi-insulating field plate before or after metallization. However, the deposition after metallization may pollute an electric furnace, and the deposition before metallization may cause the degradation of electrical performance due to the increased contact resistance between metal and silicon. Therefore, the target of the present invention is to provide a cost-effective semi-insulating field plate and a manufacturing method thereof without producing the problem of process compatibility or degradation of electrical performance.